Method of making valve tappets



Jan. 17, 1939. F. GLASSFORD METHOD OF MAKING VALVE TAPPETS Filed Jui 20,1936 INVEVNTOR 7450 GLA6FORD- ,flza ATTORNEY Patented Jan. 17, 1939UNITED STATES PATENT OFFICE METHOD OF MAKING VALVE TAPPETS ApplicationJuly 20, 1936, Serial No. 91,537

1 Claim.

This invention relates to method of forming valve tappets, for use ininternal combustion engines, gas-compressors, and analogous mechanisms.

My invention has among its objects the provision of an improvedfabricated valve tappet.

Another object of my invention resides in the provision of a novel,inexpensive, and efiicient method of forming my valve tappet.

Further objects of my invention reside in the provision of an improvedvalve tappet of low cost of manufacture and light durable structure, andin the novel combination and arrangement of parts thereof moreparticularly hereinafter described and shown in several detailedembodiments in order to illustrate the principles of my invention,reference being had to the accompanying drawing, in which:

Fig. 1 is a sectional elevational view of the tappet head before it isattached to the tappet stem.

Fig. 2 is an elevation of the blank from which the tappet stem isformed.

Fig. 3 is a tappet stem formed from the blank.

Fig. 4 is an enlarged sectional view illustrating the method ofattaching the stem to the head.

Fig. 5 is a sectional view showing a modified stem construction.

The head I0 of my improved tappet is preferably made of a high-carbonsteel or certain other metals capable of being heat treated to a highdegree of hardness and wear resistance.

The stem may be formed in various ways, but

- as shown in Fig. 2 the blank I I is a suitable length of metal tubing.Thereafter, the blank H is bored to form apertures of differentdiameters at the opposite ends, the smaller aperture I2 being threadedto receive the usual adjustment screw at l3. The larger bore I4 is ofthe diameter necessary to reduce the walls l5 tothe required thickness.The end of the tube is then flared, as shown at l6, by pressing insuitable dies, or by other means, such as spinning, so as to form anoblique flange H. The head I0 is formed having a base portion 18 and aperipheral flange portion l9 extending substantially perpendicular tothe base portion I8 to provide a recess for the reception of the flaredend 11 of the stem. The inner diameter of the flange portion I9 may bethe same diameter as the outer diameter of the flared flange I! or maybe slightly smaller when the parts are at ordinary room temperature.

The headand the stem may be united by heating the head I!) for theheat-treating process and then inserting the flared end l6 of the stemwhich is maintained at ordinary room temperature.

The raised portion H! of the head I0 is then pressed or spun while hotagainst the oblique flange H. The head end of the tappet assembly isthen quenched or cooled in the heat-treating process.

I 5 The cooling operation causes the head H] to contract in size,thereby forming an even tight fit of the raised portion [9 of the headagainst the flared end l6 of the stem. If it is desirable because of thehead and stem interlocking design to secure more clearance between theraised portion IQ of the head and the flared end I6 of the stem at thebeginning of the assembling operation, this can be accomplished bymaterially lowering the temperature of the stem as by freezing, etc.

The structure thus formed will be rigid and strong, and there will be notendency for the head to separate from the stem as these parts arefirmly interlocked and maintained permanently under stress. This resultis effected by the raised portion 19 tending to contract and the flaredend l6 tending to expand simultaneously.

The stem, as well as the head, may be formed in various ways. Forexample, by any of the usual methods of drawing a tube fro-m a sheetmetal blank. During this drawing operation the flared flange 2|] at theend of the blank is easily formed so as to be ready for engagement witha head in the aforementioned manner. Where, however, the blank is madefrom sheet metal, the walls 2! are of a substantially uniform thicknessand it may be necessary to provide a bushing 22 for the threaded end.This bushing 22 may be formed with a peripheral groove 23 into which thetube is pressed by rolling or other suitable means.

It will be understood that by forming a tappet in this manner the stemportion may be made of inexpensive material and the head portionproduced from a high carbon steel capable of being hardened when heatedand quenched. Furthermore, the stem and head portions are therebypermanently united and under stress for assembly. A material saving oftime and money is effected by using the heat-treating operation of thehead for a two-fold purpose: i. e., as a hardener and as a means forshrinking the head on the flange of the stem to produce permanentinterlocking.

If desired the outer edge of the flared flange I! may be slightlytapered so that the flange l9 may be pressed inwardly from its normalposition at right angles to the base Ill forming an acute angle betweenthe flange l9 and the base I0.

This forms an interlock between the head and stem.

My method of joining the head and the stem is such that the flange ofthe head is snug against the flange of the stem, and after bringing thehead and the stem to the same temperature they are maintainedpermanently locked under stress by the contraction of the head and theexpansion of the stem. v V

This is a great improvement over the conventional fabricated tappetwherein the membersare pressed together in various ways, as in thelatter there is a tendency for these members to recede from theirrespective positions when the pressure is withdrawn.

What I claim is:

The method of forming a tappet which comprises, forming a, radiallyextending flange portion on one end of a stem member, forming a separatehead member having body and flange portions, said head member beingformed of metal capable of being case-hardened by heat treatment,securing said head member to said stem member by forcing said flangeportion of said head member over the flange portion of said stem memberwhile maintaining a difference in temperature between said head and stemmembers by heating said head member and cooling said stem member, andimmediately quenching to harden said head member and therebysimultaneously shrinking said flange portion of said head member andexpanding said flange portion of said stem member into interlockingengagement.

FRED GLASSFORD.

